Tolerate missing role in user creation

src/PostgREST/App.hs

@@ -141,7 +141,7 @@ app dbstructure conf reqBody dbrole req =
           encode . object $ [("message", String "Failed to parse user.")]
         Just u -> do
           _ <- addUser (cs $ userId u)
-            (cs $ userPass u) (cs $ userRole u)
+            (cs $ userPass u) (cs <$> userRole u)
           return $ responseLBS status201
             [ jsonH
             , (hLocation, "/postgrest/users?id=eq." <> cs (userId u))